Implement ServiceBase using a new PersistentTaskGroup

src/frequenz/core/asyncio/__init__.py

@@ -0,0 +1,33 @@
+# License: MIT
+# Copyright © 2024 Frequenz Energy-as-a-Service GmbH
+
+"""General purpose async tools.
+
+This module provides general purpose async tools that can be used to simplify the
+development of asyncio-based applications.
+
+The module provides the following classes and functions:
+
+- [cancel_and_await][frequenz.core.asyncio.cancel_and_await]: A function that cancels a
+  task and waits for it to finish, handling `CancelledError` exceptions.
+- [PersistentTaskGroup][frequenz.core.asyncio.PersistentTaskGroup]: An alternative to
+  [`asyncio.TaskGroup`][] to manage tasks that run until explicitly stopped.
+- [Service][frequenz.core.asyncio.Service]: An interface for services running in the
+  background.
+- [ServiceBase][frequenz.core.asyncio.ServiceBase]: A base class for implementing
+  services running in the background.
+- [TaskCreator][frequenz.core.asyncio.TaskCreator]: A protocol for creating tasks.
+"""
+
+from ._service import Service, ServiceBase
+from ._task_group import PersistentTaskGroup
+from ._util import TaskCreator, TaskReturnT, cancel_and_await
+
+__all__ = [
+    "PersistentTaskGroup",
+    "Service",
+    "ServiceBase",
+    "TaskCreator",
+    "TaskReturnT",
+    "cancel_and_await",
+]